hey i just had that problem on my 92 scort, it would idle real lowat stoplights. i tried everything, than i noticed that there was a small crack in my intake tube that goes to the throttle body. The crack was on the bottom so i couldn´t see it right away. A small crack in it will make it run like crap when idling. check your intake hose for cracks. I just had the same problem your having to a tee, and i found i had a crack in it so i put some duct tape around it for temporary till i got a new hose. you should see an instant improvement when you close up the crack. let us know if what you find out, hope thats all it is
Most luckely it´s a MAF. I asked some guy and he said that MAF as well as O2 sensors have to be changed every 60k becasue they are burning like a matches. Well like light bulbs. Becasue they are light bulbs only not in vacuum but air.
won´t the MAF come up in the engine code if some thing is wrong with it. if you check your codes it should come up wouldn´t it. the problem i had like his did not come up as a code, it said there was nothing wrong. it could be the MAF but thought i would suggest something else to check cause it happened to me on both my gt´s, just something to look into.
The funniest part..It´ll not( except when it´ll totally burn out. Normally it doesn´t happend. I´m figting with my MAF right now. Because of my Ram air I´m getting wrong mixture on low rpms. Idle is not stable and sometimes it missfiering on low rpms(.
Since he has a ´97 with no idle air screw or other relevant adjustments, I´d say it´s a vacuum leak somewhere. Just remember to check the hoses to and from the EGR valve (one is underneath), the PCV valve and hose, and the condition of all the other hoses. The VECI label on the hood gives you a good idea of what hoses run where. Checking your timing belt MIGHT be worth it, but if your timing was off the performance of the engine would be off at EVERY speed/condition.